Absolutely not a doctor (or even really know what I'm talking about), but I've been hunting down a sleep disorder I've been dealing with for a decade+, and there's at least a couple of things to consider (someone please correct me if I got anything wrong)
My understanding is that during the day (evening?), your melatonin level increases. While you sleep, it goes down. If you wake up for any reason just a few hours before your optimal sleepy time, it might be a lot harder to get back to sleep.
A lot of stuff might cause you to wake up early. Very common ones, especially in the US: GERD and sleep apnea. You end up waking up, you're not tired, but you didn't get the sleep you needed.
The last part I was told only recently and I dunno how accurate it is, but supposedly you get most of your important REM sleep in the last few hours of sleep, so there's a pretty big difference between 6 and 8 hours, even though you might wake up (for reasons such as the ones above) but not be functioning at your fullest. And while you might be functioning on par with your colleagues...maybe you'd just be a total badass if you sleep better/more...
My understanding is that during the day (evening?), your melatonin level increases. While you sleep, it goes down. If you wake up for any reason just a few hours before your optimal sleepy time, it might be a lot harder to get back to sleep.
A lot of stuff might cause you to wake up early. Very common ones, especially in the US: GERD and sleep apnea. You end up waking up, you're not tired, but you didn't get the sleep you needed.
The last part I was told only recently and I dunno how accurate it is, but supposedly you get most of your important REM sleep in the last few hours of sleep, so there's a pretty big difference between 6 and 8 hours, even though you might wake up (for reasons such as the ones above) but not be functioning at your fullest. And while you might be functioning on par with your colleagues...maybe you'd just be a total badass if you sleep better/more...
Take all of this with a huge grain of salt :)